The present invention relates to an optical apparatus using an absorption saturation phenomenon of an exciton and, more particularly, to a semiconductor optical apparatus.
Various kinds of apparatus using the absorption saturation phenomenon of an exciton can be considered. In recent years, attention has been paid to the fact that excellent performance is provided by using such an apparatus as an optical recording apparatus. By realizing the absorption saturation phenomenon of an exciton by using a semiconductor super-lattice structure, a rewritable non-volatile information recording apparatus having a high speed and a high density can be realized at room temperatures.
As a method of increasing recording density by using the absorption saturation phenomenon, an optical data recording system using wavelength dimensions has been disclosed in U.S. Pat. No. 4,101,976. According to this conventional system, a bulk material which causes the saturation of a uniform absorption line and shows a heterogeneous absorption line extent is included. Porphyrin, deuterium substituted porphyrin, phthalocyanine tetrazine, and tetraphenyl porphyrin can be mentioned as optical recording materials. Data bits are recorded by using the selective absorption saturation by a narrow band high power laser beam. That is, the above recording uses a phenomenon called an photochemical hole burning (PHB) and relates to a method of causing a narrow width absorption in a special wavelength portion in a wide heterogeneous absorption line. This absorption saturation phenomenon is accomplished in a manner such that ground state molecules of the same kind put under slightly different environments are converted into exciting state molecules in a phase and energy manner by irradiating a laser beam of a special wavelength, thereby finally causing a bleaching of the ground state molecules. Therefore, in principle, the above phenomenon is operable only at super low temperatures of about 20.degree. K. or less and can be caused only by irradiating a laser beam of a high intensity. Therefore, when recording bit information, it has been known that since a high power laser beam of about, e.g., 10 W/.mu.m.sup.2 is irradiated for a period of time of at least 1 msec or longer and the recorded information is rewritten by heating, it takes a time of 5 to 10 minutes to completely erase the recorded information.
As mentioned above, in optical information recording using PHB, the phenomenon at super low temperatures of 20.degree. K. or less, preferably absolute zero, is essentially used; a high laser power is required to write information; and the information is erased or written by heating; so that there is a problem such that the apparatus enlarges in size and becomes complicated.
On the other hand, a recording density of an existing non-volatile memory is relatively so small to be 1.times.10.sup.6 to 4.times.10.sup.6 bits/cm.sup.2. Even in the present large scale computers as well, as super large computers which will be able to be used in the future for AI (artificial intelligence) or the like, a memory having a satisfactory memory capacity does not exist. It is demanded to realize a high performance non-volatile memory.
It is an object of the present invention to solve the problems of the foregoing conventional techniques and to provide an optical recording apparatus to realize super high density non-volatile information recording which can perform high speed recording, reproduction, and erasure even at temperatures near room temperature and even by the light irradiation of a low intensity.